I have tried the Harmonic Recovery Systems box in both tube and transistor setups. When I read the overwhelmingly positive review in Stereophile of this black box a few years back, I was intrigued, but the author couldn't explain the "how or why" of the box. Neither can I but he and I agree that it is not just a minor amplification process. There is what I would call an enriched or deeper soundstage with slightly more detail when the HRS is installed that cannot be attributed to just an increase in volume. It depends on where you place the box as to its effect on the music. Best palcement is between preamp and amp. In my transistor setup you can definitely hear a difference, but only you can determine if that difference is for you. In my tube setup, you can hear the difference too. But as I am moving to XLR's and the HRS only has RCA's, I have moved it to different parts of the chain will less pleasing results, but results that are noticed nonetheless. And it is another box that has to be placed somewhere, albeit a smallish one. Is it worth the trouble or cost? To me the answer is yes especially in light of what we pay for better preamps, amps, cables, etc. in our search for the "right" sound. I would buy used and try it if you are interested. But I am guessing that the effect gained decreases as the quality and cost (as well as system balance or synergy) of your system increases, so that a $10K system will gain more effect than a $40K front end. I've got both and this is a real world observation.